The present invention relates to a semiconductor device, which can be preferably used in, for example, a semiconductor device that isolates a transmitter and a receiver from each other
A sequence control that controls production equipments according to a predetermined procedure has been extensively used. Power supplies used for those production equipments are frequently very high in voltage. On the other hand, a control signal is supplied to those production equipments, and a high-voltage power supply is required for a control device. That is, it is sufficient to supply a power supply for operating a logic circuit included in the control device to the control device. Under those circumstances, there is used an isolator circuit (isolator) that transmits the control signal while isolating power supply regions different in voltage from each other.
Also, it is conceivable that a variety of noises are generated under the environment where the insulator circuit is used, and the insulator circuit that precisely transmits the control signal without being affected by those noises is demanded.
Japanese Unexamined Patent Application Publication No. 2003-142996 discloses a differential signal receiver circuit (insulator circuit) that transmits a digital signal using a differential signal. The insulator circuit disclosed in Japanese Unexamined Patent Application Publication No. 2003-142996 isolates a transmitter side from a receiver side using a photocoupler.
Further, U.S. Pat. No. 7,755,400 and Japanese Unexamined Patent Application Publication No. 2010-16815 disclose insulator circuits that isolate the transmitter side and the receiver side from each other using a capacitor. In order to realize the transmission of a direct current signal (DC signal), the insulator circuits disclosed in these patent documents separate a DC signal path and an alternating current signal (AC signal) path from each other. Also, in order to realize the transmission of the DC signal, a pulse signal is added on the transmitter side, and the added pulse signal is removed on the receiver side.
In this example, when a potential of one electrode is changed, the capacitor can transmit the change to the other electrode (AC signal can be transmitted). However, the DC signal having no change in the potential cannot be transmitted to the other electrode. For that reason, the above-mentioned configuration (separation of the paths, addition of the pulse signal) is required for the insulator circuits disclosed in U.S. Pat. No. 7,755,400 and Japanese Unexamined Patent Application Publication No. 2010-16815.